Current progress on development of respiratory syncytial virus vaccine

Human respiratory syncytial virus (HRSV) is a major cause of upper and lower respiratory tract illness in infants and young children worldwide. Despite its importance as a respiratory pathogen, there is currently no licensed vaccine for prophylaxis of HRSV infection. There are several hurdles complicating the development of a RSV vaccine: 1) incomplete immunity to natural RSV infection leading to frequent re-infection, 2) immature immune system and maternal antibodies of newborn infants who are the primary subject population, and 3) imbalanced Th2-biased immune responses to certain vaccine candidates leading to exacerbated pulmonary disease. After the failure of an initial trial featuring formalin-inactivated virus as a RSV vaccine, more careful and deliberate efforts have been made towards the development of safe and effective RSV vaccines without vaccine-enhanced disease. A wide array of RSV vaccine strategies is being developed, including live-attenuated viruses, protein subunit-based, and vector-based candidates. Though licensed vaccines remain to be developed, our great efforts will lead us to reach the goal of attaining safe and effective RSV vaccines in the near future.     

Potential therapeutic implications of new insights into respiratory syncytial virus disease

Viral bronchiolitis is the most common cause of hospitalization in infants under 6 months of age, and 70% of all cases of bronchiolitis are caused by respiratory syncytial virus (RSV). Early RSV infection is associated with respiratory problems such as asthma and wheezing later in life. RSV infection is usually spread by contaminated secretions and infects the upper then lower respiratory tracts. Infected cells release proinflammatory cytokines and chemokines, including IL-1, tumor necrosis factor-alpha, IL-6, and IL-8. These activate other cells and recruit inflammatory cells, including macrophages, neutrophils, eosinophils, and T lymphocytes, into the airway wall and surrounding tissues. The pattern of cytokine production by T lymphocytes can be biased toward 'T-helper-1' or 'T-helper-2' cytokines, depending on the local immunologic environment, infection history, and host genetics. T-helper-1 responses are generally efficient in antiviral defense, but young infants have an inherent bias toward T-helper-2 responses. The ideal intervention for RSV infection would be preventive, but the options are currently limited. Vaccines based on protein subunits, live attenuated strains of RSV, DNA vaccines, and synthetic peptides are being developed; passive antibody therapy is at present impractical in otherwise healthy children. Effective vaccines for use in neonates continue to be elusive but simply delaying infection beyond the first 6 months of life might reduce the delayed morbidity associated with infantile disease.     

Potential therapeutic implications of new insights into respiratory syncytial virus disease

Viral bronchiolitis is the most common cause of hospitalization in infants under 6 months of age, and 70% of all cases of bronchiolitis are caused by respiratory syncytial virus (RSV). Early RSV infection is associated with respiratory problems such as asthma and wheezing later in life. RSV infection is usually spread by contaminated secretions and infects the upper then lower respiratory tracts. Infected cells release proinflammatory cytokines and chemokines, including IL-1, tumor necrosis factor-α, IL-6, and IL-8. These activate other cells and recruit inflammatory cells, including macrophages, neutrophils, eosinophils, and T lymphocytes, into the airway wall and surrounding tissues. The pattern of cytokine production by T lymphocytes can be biased toward 'T-helper-1' or 'T-helper-2' cytokines, depending on the local immunologic environment, infection history, and host genetics. T-helper-1 responses are generally efficient in antiviral defense, but young infants have an inherent bias toward T-helper-2 responses. The ideal intervention for RSV infection would be preventive, but the options are currently limited. Vaccines based on protein subunits, live attenuated strains of RSV, DNA vaccines, and synthetic peptides are being developed; passive antibody therapy is at present impractical in otherwise healthy children. Effective vaccines for use in neonates continue to be elusive but simply delaying infection beyond the first 6 months of life might reduce the delayed morbidity associated with infantile disease.     

单克隆抗体在呼吸道合胞病毒感染诊断和防治中的应用

呼吸道合胞病毒 (RSV)是世界范围内婴幼儿下呼吸道感染的重要病原 ,目前尚无成熟疫苗应用于临床。展开对RSV被动免疫的研究显得尤为重要。单克隆抗体成为深入研究和防治RSV感染的有力武器。本文综述了单克隆抗体在RSV感染的诊断、预防和治疗中的应用     

Passive transfer of respiratory syncytial virus (RSV) antiserum suppresses the immune response to the RSV fusion (F) and large (G) glycoproteins expressed by recombinant vaccinia viruses.

In young infants who possess maternally derived respiratory syncytial virus (RSV) antibodies, the antibody response to RSV glycoproteins is relatively poor, despite extensive replication of RSV. In the present study, it was found that cotton rat RSV hyperimmune antiserum suppressed the antibody response to the RSV glycoproteins but not the response to vaccinia virus antigens when the antiserum was passively transferred to cotton rats prior to infection with vaccinia recombinant viruses expressing the RSV envelope glycoproteins. The cotton rats which had their immune responses suppressed by passively transferred antibodies were more susceptible to infection with RSV than were animals inoculated with control serum lacking RSV antibodies. Furthermore, many of the immunosuppressed animals infected with the vaccinia recombinant viruses developed RSV glycoprotein antibodies which had abnormally low neutralizing activities. Thus, preexisting serum RSV antibodies had dramatic quantitative and qualitative effects on the immune response to RSV glycoproteins, which may explain, in part, the poor RSV antibody response of young human infants to infection with RSV. Our observations also suggest that immunosuppression by preexisting, passively acquired RSV antibodies may constitute a major obstacle to RSV immunoprophylaxis during early infancy, when immunization is most needed.     

Cytokine (tumor necrosis factor, IL-6, and IL-8) production by respiratory syncytial virus-infected human alveolar macrophages.

Human alveolar macrophages (AM) are susceptible to infection with respiratory syncytial virus (RSV), but the infection is abortive after the initial cycles of virus replication. We have investigated if RSV infection of AM results in the production of cytokines TNF, IL-6, and IL-8, all of which may modulate inflammatory and immune responses to the virus, as well as may directly protect respiratory epithelial cells against spread of infection. Within 1 h after interaction with RSV, increased mRNA levels were found for all three cytokines. Peak expression of the mRNAs occurred at 3 to 6 h. The virus most effectively induced TNF mRNA expression greater than IL-6 mRNA greater than IL-8 mRNA, as compared to cytokine mRNA expression induced by bacterial endotoxin. Inactivated virus was almost as effective as live virus in inducing and maintaining increased IL-6 and IL-8 mRNA over 16 h, whereas live infectious RSV was necessary for maintaining TNF mRNA expression over the same time. Protein concentrations of the different cytokines in the supernatants of infected AM reflected the increased levels of mRNA in the cells. Despite the high levels of cytokines with possible antiviral activity (TNF and IL-6) in the AM supernatants, neither supernatants nor rTNF when added to bronchial epithelial cells protected them from infection with RSV. However, TNF, IL-1, and RSV, but not IL-6, induced IL-8 and IL-6 mRNA expression by the bronchial epithelial cells suggesting that cytokines produced by RSV-infected AM may be more important in modulating the inflammatory response in infection than directly interfering with virus infection/replication of airway epithelium.     

呼吸道合胞病毒非结构蛋白NS1、NS2的研究进展

呼吸道合胞病毒(reespiratory syncytial virus,RSV)是引起婴幼儿和老年人下呼吸道感染的重要病原体之一.由于该病毒的致病机理还不太清楚导致目前尚无有效治疗RSV的方法.研究表明,呼吸道合胞病毒的非结构蛋白NS1、NS2具有抗细胞凋亡的作用,同时可以逃避宿主免疫系统(IFN)对病毒的干扰,有利于病毒复制.敲除这两种基因的减毒活疫苗和袁达沉默NS1的小干扰RNA(siRNA)的质粒研究已经取得了一定的进展.对非结构蛋白功能的深入研究有助于了解RSV的致病机理,同时为预防和治疗RSV感染奠定理论基础.     

人呼吸道合胞病毒活疫苗研究进展

人呼吸道合胞病毒是引起婴幼儿支气管炎和肺炎的主要原因,也可导致免疫缺陷病人及老年人群显著发病和死亡.人呼吸道合胞病毒疫苗已被世界卫生组织(World Health Organization,WHO)列为全球最优先发展的疫苗之一.经过50多年的研究,尤其是随着重组技术和反向遗传学的出现,对RSV疫苗的研究取得了重要进展,...     

Long-Term Shedding of Influenza Virus,Parainfluenza Virus,Respiratory Syncytial Virus and Nosocomial Epidemiology in Patients with Hematological Disorders

Respiratory viruses are a cause of upper respiratory tract infections (URTI), but can be associated with severe lower respiratory tract infections (LRTI) in immunocompromised patients. The objective of this study was to investigate the genetic variability of influenza virus, parainfluenza virus and respiratory syncytial virus (RSV) and the duration of viral shedding in hematological patients. Nasopharyngeal swabs from hematological patients were screened for influenza, parainfluenza and RSV on admission as well as on development of respiratory symptoms. Consecutive swabs were collected until viral clearance. Out of 672 tested patients, a total of 111 patients (17%) were infected with one of the investigated viral agents: 40 with influenza, 13 with parainfluenza and 64 with RSV; six patients had influenza/RSV or parainfluenza/RSV co-infections. The majority of infected patients (n = 75/111) underwent stem cell transplantation (42 autologous, 48 allogeneic, 15 autologous and allogeneic). LRTI was observed in 48 patients, of whom 15 patients developed severe LRTI, and 13 patients with respiratory tract infection died. Phylogenetic analysis revealed a variety of influenza A(H1N1)pdm09, A(H3N2), influenza B, parainfluenza 3 and RSV A, B viruses. RSV A was detected in 54 patients, RSV B in ten patients. The newly emerging RSV A genotype ON1 predominated in the study cohort and was found in 48 (75%) of 64 RSV-infected patients. Furthermore, two distinct clusters were detected for RSV A genotype ON1, identical RSV G gene sequences in these patients are consistent with nosocomial transmission. Long-term viral shedding for more than 30 days was significantly associated with prior allogeneic transplantation (p = 0.01) and was most pronounced in patients with RSV infection (n = 16) with a median duration of viral shedding for 80 days (range 35–334 days). Long-term shedding of respiratory viruses might be a catalyzer of nosocomial transmission and must be considered for efficient infection control in immunocompromised patients.     

Respiratory syncytial virus infection suppresses lung CD8+ T-cell effector activity and peripheral CD8+ T-cell memory in the respiratory tract.

Respiratory syncytial virus (RSV) is a major cause of morbidity from respiratory infection in infants, young children and the elderly. No effective vaccine against RSV is currently available and studies of the natural history of RSV infection suggest repeated infections with antigenically related virus strains are common throughout an individual's lifetime. We have studied the CD8+ T-cell response during experimental murine RSV infection and found that RSV inhibits the expression of effector activity by activated RSV-specific CD8+ T cells infiltrating the lung parenchyma and the development of pulmonary CD8+ T-cell memory by interfering with TCR-mediated signaling. These data suggest a possible mechanism to explain the limited duration of protective immunity in RSV infection.     

Chinchilla and murine models of upper respiratory tract infections with respiratory syncytial virus

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infections in infants and the elderly. While the primary infection is the most serious, reinfection of the upper airway throughout life is the rule. Although relatively little is known about either RSV infection of the upper respiratory tract or host mucosal immunity to RSV, recent literature suggests that RSV is the predominant viral pathogen predisposing to bacterial otitis media (OM). Herein, we describe mouse and chinchilla models of RSV infection of the nasopharynx and Eustachian tube. Both rodent hosts were susceptible to RSV infection of the upper airway following intranasal challenge; however, the chinchilla proved to be more permissive than the mouse. The chinchilla model will likely be extremely useful to test the role of RSV in bacterial OM and the efficacy of RSV vaccine candidates designed to provide mucosal and cytotoxic T-lymphocyte immunity. Ultimately, we hope to investigate the relative ability of these candidates to potentially protect against viral predisposal to bacterial OM.     

Blocking intercellular adhesion molecule-1 on human epithelial cells decreases respiratory syncytial virus infection

The respiratory syncytial virus (RSV) causes potentially fatal lower respiratory tract infection in infants. The molecular mechanism of RSV infection is unknown. Our data show that RSV colocalizes with intercellular adhesion molecule-1 (ICAM-1) on the HEp-2 epithelial cell surface. Furthermore, a neutralizing anti-ICAM-1 mAb significantly inhibits RSV infection and infection-induced secretion of proinflammatory chemokine RANTES and mediator ET-1 in HEp-2 cells. Similar decrease in RSV infection is also observed in A549, a type-2 alveolar epithelial cell line, and NHBE, the normal human bronchial epithelial cell line when pretreated with anti-ICAM-1 mAb prior to RSV infection. Incubation of virus with soluble ICAM-1 also significantly decreases RSV infection of epithelial cells. Binding studies using ELISA indicate that RSV binds to ICAM-1, which can be inhibited by an antibody to the fusion F protein and also the recombinant F protein can bind to soluble ICAM-1, suggesting that RSV interaction with ICAM-1 involves the F protein. It is thus concluded that ICAM-1 facilitates RSV entry and infection of human epithelial cells by binding to its F protein, which is important to viral replication and infection and may lend itself as a therapeutic target.     

Innate immune recognition of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the leading cause of respiratory infection in infants and young children. Severe clinical manifestation of RSV infection is a bronchiolitis, which is common in infants under six months of age. Recently, RSV has been recognized as an important cause of respiratory infection in older populations with cardiovascular morbidity or immunocompromised patients. However, neither a vaccine nor an effective antiviral therapy is currently available. Moreover, the interaction between the host immune system and the RSV pathogen during an infection is not well understood. The innate immune system recognizes RSV through multiple mechanisms. The first innate immune RSV detectors are the pattern recognition receptors (PRRs), including toll-like receptors (TLRs), retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), and nucleotide-biding oligomerization domain (NOD)-like receptors (NLRs). The following is a review of studies associated with various PRRs that are responsible for RSV virion recognition and subsequent induction of the antiviral immune response during RSV infection. [BMB Reports 2014; 47(4): 184-191]     

HLA class I-restricted cytotoxic T-cell epitopes of the respiratory syncytial virus fusion protein

Virus-specific cytotoxic T lymphocytes (CTL) play a major role in the clearance of respiratory syncytial virus (RSV) infection. We have generated cytotoxic T-cell clones (TCC) from two infants who had just recovered from severe RSV infection. These TCC were functionally characterized and used to identify HLA class I (B57 and C12)-restricted CTL epitopes of RSV.     

Antimicrobial activity of lipids added to human milk,infant formula,and bovine milk

Lipids previously shown to have antiviral and antibacterial activity in buffers were added to human milk, bovine milk, and infant formulas to determine whether increased protection from infection could be provided to infants as part of their diet. Fatty acids and monoglycerides with chain lengths varying from 8 to 12 carbons were found to be more strongly antiviral and antibacterial when added to milk and formula than long chain monoglycerides. Lipids added to milk and formula inactivated a number of pathogens including respiratory syncytial virus (RSV), herpes simplex virus type 1 (HSV-1), Haemophilus influenzae, and Group B streptococcus. The results presented in this study suggest that increased protection from infection may be provided to infants at mucosal surfaces, prior to the digestion of milk and formula triglycerides, by the addition of antimicrobial medium chain monoglycerides to an infant's diet.     

Plasma interferon-gamma, interleukin-10 and soluble markers of immune activation in infants with primary adenovirus (ADV) and respiratory syncytial virus (RSV) infection

Adenovirus (ADV) and respiratory syncytial virus (RSV) are etiological agents of acute respiratory tract infection in infants. Long-term prognosis of ADV infection includes severe lung damage, bronchiectasis and hyperlucent lung, while RSV infection is associated with development of recurrent wheezing and subsequent asthma. These differences may be related to differences in the primary immune responses elicited by these viruses. In this paper, we investigated the type of cytokine responses and the magnitude of immune activation in ADV and RSV infections in infants. We examined plasma concentrations of interferon-gamma (IFN-gamma), interleukin-10 (IL-10), soluble interleukin-2 receptor (sCD25) and soluble tumor necrosis factor receptor II (sTNFR-II) in previously healthy infants during the acute phase of primary ADV infection (n = 21) and RSV infection (n = 68), and in uninfected controls (n = 44). In ADV-infected infants, IFN-gamma plasma levels were significantly higher than those observed in RSV cases and the control group (p < 0.05). RSV cases did not show any differences in IFN-gamma plasma levels compared to the other groups. sCD25 levels were significantly higher in ADV- and RSV-infected infants than in controls (p < 0.0001), and higher in ADV than in RSV cases (p < 0.05). sTNFR-II levels were significantly higher in RSV- and ADV-infected infants than in controls (p < 0.0001, p < 0.05, respectively), and higher in RSV than in ADV infection (p < 0.05). No significant differences were observed in IL-10 plasma concentrations between the three groups. These results indicate that ADV and RSV infections in infants differ significantly with regard to the magnitude of production of interferon-gamma and soluble immune activation markers sCD25 and sTNFR-II. These immunological differences may be involved in the different clinical outcomes associated with these viral infections.     

Respiratory Syncytial Virus Can Infect Basal Cells and Alter Human Airway Epithelial Differentiation

Respiratory syncytial virus (RSV) is a major cause of morbidity and mortality worldwide, causing severe respiratory illness in infants and immune compromised patients. The ciliated cells of the human airway epithelium have been considered to be the exclusive target of RSV, although recent data have suggested that basal cells, the progenitors for the conducting airway epithelium, may also become infected in vivo. Using either mechanical or chemical injury models, we have demonstrated a robust RSV infection of p63⁺ basal cells in air-liquid interface (ALI) cultures of human bronchial epithelial cells. In addition, proliferating basal cells in 2D culture were also susceptible to RSV infection. We therefore tested the hypothesis that RSV infection of this progenitor cell would influence the differentiation status of the airway epithelium. RSV infection of basal cells on the day of seeding (MOI≤0.0001), resulted in the formation of an epithelium that showed a profound loss of ciliated cells and gain of secretory cells as assessed by acetylated α-tubulin and MUC5AC/MUC5B immunostaining, respectively. The mechanism driving the switch in epithelial phenotype is in part driven by the induced type I and type III interferon response that we demonstrate is triggered early following RSV infection. Neutralization of this response attenuates the RSV-induced loss of ciliated cells. Together, these data show that through infection of proliferating airway basal cells, RSV has the potential to influence the cellular composition of the airway epithelium. The resulting phenotype might be expected to contribute towards both the severity of acute infection, as well as to the longer-term consequences of viral exacerbations in patients with pre-existing respiratory diseases.     

Neutralizing anti-F glycoprotein and anti-substance P antibody treatment effectively reduces infection and inflammation associated with respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the most important virus mediating lower respiratory tract illness in infants and young children. RSV infection is associated with pulmonary inflammation and increased levels of substance P (SP), making the airways and leukocytes that express SP receptors susceptible to the proinflammatory effects of this peptide. This study examines combining neutralizing anti-F glycoprotein and anti-SP antibody treatment of RSV-infected BALB/c mice to inhibit RSV replication and inflammation associated with infection. BALB/c mice were prophylactically treated with antibody prior to RSV infection or were therapeutically treated at day 2 or 6 post-RSV infection. Prophylactic or therapeutic treatment with anti-SP antibodies promptly reduced pulmonary inflammatory cell infiltration and decreased the number of cells expressing proinflammatory cytokines, while anti-F antibody treatment reduced virus titers. The results suggest that combined anti-viral and anti-SP antibody treatment may be effective in treating RSV disease.